by Kent Somers, USA TODAY Sports

by Kent Somers, USA TODAY Sports

It was never a question of if the Cardinals were going to sign Patrick Peterson to a contract extension. It was when.

And it turned out to be sooner than many people expected. Peterson and the Cardinals announced Tuesday even they had agreed to terms on a five-year extension that is expected to make Peterson the highest paid cornerback in the NFL.

Peterson tweeted that the deal is worth $70 million, $48 of which is guaranteed. The $15 million yearly average would be the highest of any cornerback.

Peterson, now under contract through the 2020 season, will have a press conference on Wednesday morning.

Peterson is the first player taken in the first round of the 2011 to agree to a contract extension. That class was the first to enter the NFL under the current collective bargaining agreement, which placed limitation on rookie contracts.

That presented considerable obstacles to reaching a contract extension. Talks between Cardinals General Manager Steve Keim and his staff and Peterson's agents, Joel Segal and Chafie Fields, heated up in recent days, and the final hurdles were cleared on Tuesday.

Retaining Peterson, a three-time Pro Bowler, was a key to the Cardinals future. The Cardinals were believed to be about $11 million under the salary cap before Peterson's extension, and his salary cap figures for the coming years at not yet known.

Contracts don't become official until approved by the NFL office, and the exact parameters of the deal likely won't be known for a few days.

Peterson was drafted fifth overall in 2011, and had two years left on his first NFL contract.

Beginning in 2011, players taken in the first round sign four-year contracts, with the teams having an option for a fifth year. The Cardinals exercised that option with Peterson.

First-round picks also weren't eligible for contract extensions until the completion of their third seasons.

Those factors complicate negotiations, which is why no first-round pick from 2011 had agreed to a contract before Peterson.

Included in that group are some of the best players in the NFL, including Rams defensive end Robert Quinn, Houston defensive lineman J.J. Watt and Bengals receiver A.J. Green.

A new contract for Peterson had to make financial sense for the Cardinals since they had him under contract for two more seasons. But on the flip side, signing Peterson a year or two from now would cost the Cardinals considerably more.

Peterson, who has made the Pro Bowl twice as a cornerback and once as a returner, was due to make $2.9 million in salary this year and $10 million a year from now.

Peterson, 24, has never missed a game, starting all 48 in which he played. He has 162 tackles and 12 interceptions. As a rookie, he returned four punts for touchdowns, but after two sub-par years as a returner, Peterson has been replaced by Ted Ginn, Jr., who signed as a free agent this off-season.